Which of the Following Is an Advantage of an Allosteric

Which of the following is an advantage of an allosteric drug compared to an orthosteric one?

A) they can modulate their effect in a more subtle way
B) an allosteric drug may be more specific for a specific reaction than one that binds to the receptor itself
C) they may be safer as they have no effect at all unless the natural substrate is present
D) all of these are advantages
E) none of these is an advantage